Electrodepositable photoresist compositions are generally known in the art. In a broad sense, the art has described photosensitive electrodepositable compositions which are intended to produce permanently adhering films. The art relating to such permanent films, such as paints, is non-informing in the area of photoresist compositions.
Of interest here, are photoresist compositions that form photoimages such as printed circuits or lithographic printing plates. In essence, photoresist compositions form films which are either insolubilized or solubilized with an energy source such as actinic irradiation using a photomask. The use of a mask enables selective irradiation of unmasked areas of the films. The films are then developed by removing the masked or unmasked areas thereof depending on whether the photoresist is negative or positive, respectively.
Electrodeposition of photoresist compositions poses several problems. Some of the shortcomings of the known electrodepositable photoresist compositions reside in problems of tackiness or stickiness and/or the associated problems of poor light sensitivity and resolution. Films of known compositions tend to stick or otherwise adhere to photomasks that are placed on them in the process of producing the required pattern. The photomask (or phototool) is a self-supporting film on which is imposed a pattern of the desired image, or the negative thereof, which is transferred to a substrate. Removal of a photomask from a sticky film can damage the photoresist and/or photomask. The damaged photoresist thus causes an unacceptable image transfer and, consequently, defects in the final products. The damaged photomask becomes unacceptable for subsequent use, thus increasing the cost of production.
The prior art, in an attempt to overcome the above problems, employs cover sheets, such as a Mylar sheet, or coatings which are typically placed over photoresists in order to prevent sticking of the photomasks to photoresists. However, the presence of cover sheets or coatings adversely affects resolution of the image because the mask is thus spaced from the photoresist and incident light is diffracted as it passes through the mask and the cover sheet or coating. The diffraction or "spreading" of the incident light becomes more pronounced as the distance between the photomask and the photoresist increases. Photosensitivity can also be adversely affected if the cover sheet or coating absorbs any of the incident light.
By the present invention, non-tacky photoresist compositions are provided that do not require a cover sheet or coating and provide good photosensitivity and image resolution.